xy+x+y=11 x^2y+xy^2=30 xy(x+y)=30xy,x+y为方程x^2-11x+30=0两个根(x-5)(x-6)=0xy=5,x+y=6或xy=6,x+y=51)xy=5,x+y=6x,y是方程x^2-6x+5=0两个根x=1,y=5或x=5,y=12)xy=6,x+y=5x,y是方程x^2-5x+6=0两个根x=2,y=3或x=3,...